FR2945331A1 - VIROLE FOR AIRCRAFT TURBOOMOTOR STATOR WITH MECHANICAL LOADING DUCKS OF AUBES. - Google Patents

Abstract

The invention relates to a ferrule (16a) for an aircraft turbine engine module stator provided with a plurality of through apertures (22) each intended to receive a stator blade (4), each aperture defining a skeleton ( 32) extending between a first end (25) for accommodating the trailing edge (26) of the blade and a second end (27) for accommodating the leading edge (28) of the blade. According to the invention, at least one of the openings (22) is associated with a mechanical unloading slot (36) made through the ferrule and arranged opposite and at a distance from the first end (25) of the opening. according to the direction of the skeleton (32).

Description

VIROLE FOR AIRBORNE AIRCRAFT TURBOMOTOR WITH MECHANICAL UNLOADING DUCTS OF AUBES DESCRIPTION

The present invention relates generally to an aircraft turbine engine, preferably of the turbojet or turboprop type. More particularly, the invention relates to a stator part for a module of such a turbine engine, this part comprising a plurality of stator vanes as well as two concentric rings carrying the vanes 15 and intended to delimit radially a primary flow through this turbine engine, respectively inward and outward. The invention also relates to these ferrules delimiting the primary flow. In order to maintain the stator vanes extending radially inwardly from the outer shell, the latter usually comprises a plurality of circumferentially spaced, and through-made, openings, each of which is practiced in the outer shell. the thickness of the ferrule, generally metallic. Each aperture houses the head of one of the stator vanes, this head being attached to the outer ferrule by means of a solder made in the aperture concerned, extending continuously all around the head of the stator. Similarly, in order to maintain the stator vanes extending radially outwardly from the inner ferrule, the ferrule usually comprises a plurality of circumferentially spaced apertures from each other, and made through. Each ajour accommodates the foot of one of the stator vanes, this foot being fixed to the outer ferrule by means of a solder made in the aperture concerned, extending continuously all around the head of the stator. dawn. This design, however widespread in the field, has the disadvantage of frequently appear cracks at the trailing edge of the blade head and / or the trailing edge of the blade root. The explanation of this phenomenon harmful to the life of the stator blades lies in the presence of very large static charges at the trailing edge of the blade head and / or the blade root, which translate into a dynamic margin too low, favoring the appearance of cracks. To overcome this drawback, it has been proposed to thicken the ferrules, so as to limit its deformations in operation, and thus to reduce the stresses applied to the trailing edges of the heads and blade roots. Nevertheless, this solution is extremely penalizing in terms of cost and mass. It has also been proposed to thicken the blades, but this inevitably leads to a disturbance of the air flow therethrough, with consequent direct negative impact on the overall performance of the turbine engine. The invention therefore aims to at least partially overcome the problem mentioned above, relating to the achievements of the prior art. To this end, the subject of the invention is a ferrule for an aircraft turbine engine module stator provided with a plurality of through apertures each intended to receive a stator vane, each aperture defining a skeleton extending between a first end for housing the edge of and a second end for attacking the blade. According to the invention, said openings is associated with a mechanical slot made through-on arranged opposite and at a distance from the end of the aperture according to the skeleton. The proposed invention generally makes it possible to reduce the static loads at the portion of the trailing edge of the blade intended to cooperate with the aperture equipped with such a mechanical unloading slot, to release the dynamic margin, and therefore to strongly delay the appearance of cracks. Thus, during the deformation of the ferrule in operation, the heavily loaded zone is offset at the ends of the slot, namely at a distance from the trailing edge, even within the shell which is largely capable of supporting this load.

The solution provided proves to be very satisfactory in that it does not generate any leakage from the dawn housing the edge to at least one of unloading the shell, and said first direction of said 4 penalty in terms of mass, cost or performance. In addition, this results in an increased blade life, advantageously involving the periods of visit / maintenance may be further spaced over time. Naturally, this specificity can be applied to all the stator vanes or only some of them, depending on the needs and constraints encountered. By way of indicative example, in the case where the ferrule according to the invention is sectorised, it has been found advisable to associate such a mechanical unloading slot only with the two vanes located at the ends of each ferrule sector. Nevertheless, any other configuration can be envisaged without departing from the scope of the invention. The realization of the mechanical unloading slots penalizes only very little the manufacturing process of the ferrule, since they can be machined at the same time as the openings. Moreover, it is advantageously possible to make such slots on already existing ferrules. Finally, it is noted that the ferrule according to the invention preferably constitutes the outer radial delimitation ferrule of the primary flow, that is to say that of the two stator ferrules which undergoes the greatest deformation in operation, under the effect displacement of the casings of the turbine engine. In this respect, it is noted that its main deformation, like that of the inner ferrule operating to a lesser extent, is characterized by a diameter increasing towards the rear, globally transforming its cylindrical shape frustoconical shape. Preferably, said slot extends along a curved line toward the aperture, which may extend around a portion thereof. Preferably, said aperture has, on either side of the skeleton, an intrados and an extrados portion joining at said first and second ends of the aperture, and said slot also extends opposite and at a distance from portions of the intrados and extrados portions which meet at said first end of the aperture. The slot may extend around the rear portion of the aperture at a distance therefrom which remains substantially constant. Preferably, said slot has a general shape of U or V inside which is arranged said first end of the aperture, for a better unloading of the trailing edge of the blade.

Preferably, said slot is filled with a filling material. The main function sought by the introduction of this material is the sealing of the air flow passing through the stator vanes, but also limits thermal losses. Thus, either this slot remains recessed, or it is filled by said filling material which exerts a zero or negligible mechanical support. It may for example be a filler material of the abradable type, for example a silicone rubber compound resistant to temperature variations, loaded with beads. Preferably, the ferrule forms a substantially continuous annular structure, preferably in one piece. Alternatively, it is achieved by the end-to-end placement of angular sectors of ferrule. The invention also relates to a stator portion for an aircraft turbine engine module comprising at least one ferrule as presented above, as well as a plurality of stator vanes.

Preferably, said ferrule is an outer ferrule, and each of the through perforations receives the head of one of said blades, fixed to the outer ferrule by a solder arranged in its opening and extending continuously all around the head of the ferrule. 'dawn. Thus, this solution makes it possible to confer a satisfactory maintenance of the blade head in the opening thanks to the continuous soldering, and to avoid overloading the trailing edge of this blade head by placing a mechanical unloading slot specific to the present invention, spaced from this trailing edge. This specificity is simultaneously or alternatively applicable to the inner shell of the stator portion. Indeed, it further comprises an inner ferrule provided with a plurality of through openings each receiving the foot of one of said vanes, fixed to the inner ferrule by a solder arranged in its ajour and extending so continue all around the dawn foot. A mechanical unloading slot can therefore be associated with one or more of these openings of the inner shell. The subject of the invention is also an aircraft turbine engine module comprising at least one stator part as described above, the module preferably being a compressor, preferably a high-pressure one, but which can alternatively be a turbine, without leaving of the scope of the invention. Finally, the invention relates to a turbine engine for aircraft comprising at least one module as described above, the turbine engine being preferably a turbojet. Other advantages and features of the invention will become apparent in the detailed non-limiting description below. This description will be made with regard to the appended drawings among which; FIG. 1 represents a partial schematic half-sectional view of a high-pressure turbine engine compressor, according to a preferred embodiment of the present invention; FIG. 2 represents a front view of an assembly forming an angular portion of the stator portion of the compressor shown in FIG. 1; - Figure 3 shows a partial top view of the assembly shown in Figure 2; FIGS. 3a and 3b show alternative embodiments for the mechanical unloading slots made on the shell of the assembly shown in FIG. 3; and FIGS. 4a and 4b show embodiments of additional mechanical unloading slots made on the shell of the assembly shown in FIG. 3. Referring firstly to FIG. part of a high pressure compressor 1 for a turbine engine, according to a preferred embodiment of the present invention. In known manner, the compressor has, alternately in an axial direction parallel to the axis 2 of the compressor, stator vanes 4 and rotor blades 6. The stator vanes 4, distributed circumferentially around the axis 2, are integrated in a stator portion 13 also object of the invention, further comprising an inner ferrule 8 of radially inner delimitation of a primary annular flow 10 passing through the turbine engine, this ferrule 8 carrying the feet of the blades 4 which pass through it . It also contains an outer ring 16 of external radial delineation of the primary annular flow 10, which carries the heads of the vanes 4 which pass therethrough. In this regard, it is noted that the stator portion also comprises known additional elements reported on the ferrule 8, such as a radially inner abradable coating 15 forming annular sealing track, contacted by a sealing device 12 carried by the rotor stage 14 carrying the rotating vanes 6 and arranged downstream of the stator portion concerned. As mentioned above, the rotating sealing device 12 is in a known manner of labyrinth or wipe type. In the preferred embodiment described, the stator portion 13 forms a substantially annular structure of axis 2, and is preferably composed by the establishment of a plurality of assemblies 20 such as that shown in FIG. each an angular or circumferential portion of this stator portion. As visible in this figure, each assembly 20 comprises an inner ferrule angular sector 8a carrying a plurality of stator vanes 4, the inner ferrule 8 resulting from the establishment, end to end, of all sectors 8a. In the segmented configuration shown, the angular sectors 8a (only one visible in FIG. 2) jointly forming the shell 8 are therefore preferably devoid of direct rigid mechanical connections connecting them to each other, their adjacent ends being in fact simply placed in position. look at each other, with or without play.

The segmentation operated for the ferrule 8 is also adopted, in an identical manner, for the abradable radially inner coating 15 forming an annular sealing track, only an angular sector 15a of this coating being thus fixedly supported by the ferrule sector 8a. In a similar manner, the assembly 20 comprises an angular sector of outer shell 16a carrying the plurality of stator vanes 4, the outer shell 16 thus resulting from the establishment of all the sectors 16a. Here again, the angular sectors 16a (only one visible in FIG. 2) jointly forming the ferrule 16 are therefore preferably devoid of direct rigid mechanical connections connecting them to each other, their adjacent ends being in fact simply placed opposite them. the others, with or without clearance. By being carried out by the end-to-end insertion of several of these angular portions 20, the stator portion 13 thus adopts a so-called segmented design, as opposed to a design also envisaged, so-called continuous, in which the ferrules 8 and 16 are each single and continuous 360 °. An alternative could also be to provide only one of the two ferrules 8 and 16 is unique and continuous 360 °, and the other shell sectorized. As an indication, it is noted that the number of assemblies / sectors 20 to form the annular stator portion 13 above may be between 6 and 14, each set 20 preferably having the same angular / circumferential extent. Referring now to Figure 3, it can be seen that the outer annular sector 16a of outer shell is provided with perforations 22 made in the thickness of this sector 16a, conferring them a character through. For reasons of clarity of the description, the openwork 22 visible on the top of FIG. 3 has been represented without its associated blade, unlike the opening 22 shown on the bottom of this same figure, receiving the head of its associated blade 4. It is rigidly attached thereto by a solder 21, 30 made continuously all around the blade head in the space 19 delimited between the lateral wall 15 of the aperture 22 and the outer surface of the aperture 22. the dawn head. Each aperture 22 has a side wall comprising an intrados portion 23 and an extrados portion 24 which meet at the two front and rear ends of the aperture. The first 25 of these two ends is intended to accommodate the trailing edge 26 of the head of the blade, while the second 27 is intended to house the leading edge 28 of the head of the blade. The intrados 23 and extrados 24 define a skeleton 32 passing through the two ends 25, 27, and corresponding in a known manner to the median line running between the intrados 23 and extrados 24 parts. Moreover, as shown on the opening of the bottom of Figure 3, the skeleton 32 of the aperture 22 is coincident with the skeleton 33 of the blade head fixed by the solder 21 in this openwork, the profiles of the aperture and the blade head being in centric and homothetic effects. One of the peculiarities of the present invention resides in the realization, in association with at least one of the openings 22, of a mechanical unloading slot 36 made through the shell, at a distance from the aperture 22 concerned, towards the rear. More specifically, the slot 36 is arranged opposite and at a distance from the first end 25 of the aperture in the direction of the skeleton 32, and are therefore spaced apart from the trailing edge of the associated blade. In the embodiment shown, the slot 36 extends along a line 38 curved towards the aperture 12, which extends around a rear portion thereof. Here, the slot 36 and the line 38 take the general shape of a U or a V, similar to a horseshoe shape, inside which is arranged the rear part of the ajour, with the first end 25 opposite and remote from the bottom of this U. In this regard, it is noted that the distance d in the direction of the skeleton 32, between the end 25 of the aperture and the slot 36, is between 0, 02 and 0.1 times, and even more preferably between 0.03 and 0.05 times the total length (not referenced) of the head of the blade 4 along this skeleton. In this configuration, the two branches of the U also extend respectively facing and at a distance from the portions 23a, 24a of the intrados 23 and extrados 24 portions which meet at the first end 25. The distance separating the branches of the U of their associated apertured portions 23a, 23b may be the same or near the distance d, implying that the slot 36 extends around the rear portion of the aperture 22 at a distance therefrom which remains substantially constant. It is stated that the branches of the U have a substantially identical length, and that the rear part of the skeleton 32 forms a substantially axis of symmetry for the U-shaped slot 36. The length 1 of the aperture 22, according to the direction of the skeleton 32, which penetrates into the U hollow, is between 0.03 and 0.4 times, and even more preferably between 0.05 and 0.2 times the total length (unreferenced) of the head of the dawn 4 along this skeleton. A first possibility lies in the fact of leaving the mechanical unloading slot 36 hollowed out, as shown in that of the top of FIG. 3. Alternatively, it could be filled by a filling material 40 essentially aimed at sealing the primary flow. that is to say to avoid leaks through the slot 36. Such a filling material is shown schematically by the reference 40 on the bottom slot of FIG. 3. It may for example be a filler material of the abradable type, for example a temperature-resistant silicone rubber compound loaded with beads.

If such a blade mechanical discharge slot 36 is preferably provided only in association with the blades located respectively at both ends of the assembly 20, it could nevertheless be otherwise, without departing from the scope of the invention. In addition, such slits 36 mechanical blade unloading could also be provided in association with the through openings of the inner shell 8, which receive the blade roots. The assembly would then be identical or similar to that shown in FIG. 3 for the outer shell. In FIG. 3a, a first alternative embodiment for the slot 36 can be seen. It has a shape generally similar to that described above, only its two ends 36a having been widened in order to reduce the stresses to which the ferrule is subjected. these slit ends. Thus, instead of presenting a substantially identical width over its entire length, the slot 36 thus integrates widened and rounded ends 36a, preferably oriented so as to move away from the aperture 22, in order to orient the stresses in a opposite direction to that of dawn. FIG. 3b shows another alternative embodiment, in which the slot 36 corresponds approximately to half of the slot shown in FIG. 3a, one of its ends 36a therefore being traversed by the skeleton 32 of the aperture 22. Si such slots 36 are associated with the trailing edge due to a large static loading of this portion of the blade, mechanical discharge similar slots could also be associated with other parts of the blade 4, also likely to be very static. This is for example the leading edge of dawn, either at the foot or the head of dawn. In such a case, an additional mechanical discharge slot 136 shown in FIG. 4a can be made to pass through the ferrule, and arranged opposite and at a distance from the second end 27 of the aperture, in the direction of the skeleton 32. such slot 136 can then take a shape similar to the slots 36 described above, being oriented towards the aperture 22, and penetrated by the front portion thereof.

Simultaneously or alternatively, it may be one or more mechanical discharge slots 236 along the intrados portion 23 and / or the extrados portion 24 of the aperture, at a distance from the portion concerned 23, 24, as shown on FIG. Figure 4b. Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely as non-limiting examples.

Claims (13)

REVENDICATIONS1. Ferrule (16) for an aircraft turbine engine module stator provided with a plurality of through apertures (22) each for receiving a stator vane (4), each aperture defining a skeleton (32) extending between a first end (25) for accommodating the trailing edge (26) of the blade and a second end (27) for accommodating the leading edge (28) of the blade, characterized in that at least one of said openings (22) is associated with a mechanical discharge slot (36) made through the ferrule, and arranged opposite and at a distance from said first end (25) of the aperture in the direction of said skeleton (32) . 2. Ferrule according to claim 1, characterized in that said slot (36) extends along a line (38) curved towards the aperture. 3. Ferrule according to claim 1 or claim 2, characterized in that said ajour (22) has, on both sides of the skeleton (32), an intrados part (23) and an extrados part (24) joining together at the level of said first and second ends (25, 27) of the aperture, and in that said slot (36) also extends opposite and at a distance from the portions (23a, 24a) of the intrados and extrados parts (23, 24) which meet at said first end (25) of the aperture (22). 17 4. Ferrule according to any one of the preceding claims, characterized in that said slot (36) has a general shape of U or V within which is arranged said first end (25) of the ajour. 5. Ferrule according to any one of the preceding claims, characterized in that said slot (36) is filled by a filling material (40). 6. Ferrule according to any one of the preceding claims, characterized in that it forms a substantially continuous annular structure. 7. Ferrule according to any one of claims 1 to 5, characterized in that it forms a substantially annular structure formed by the establishment end to end angular sectors ferrule (16a). 8. A stator part (13) for an aircraft turbine engine module comprising at least one ferrule (16) according to any one of the preceding claims, and a plurality of stator vanes (4). 9. The stator portion according to claim 8, characterized in that said ferrule is an outer ferrule (16), and in that each of the through openings (22) receives the head of one of said vanes (4), fixed to the outer shell by a solder (21) arranged in its opening and extending continuously all around the blade head (4). 10. A stator portion according to claim 9, characterized in that it further comprises an inner shell (8) provided with a plurality of through holes each receiving the foot of one of said vanes (4), fixed to the inner shell by a solder arranged in its opening and extending continuously all around the blade root. 11. Module (1) of an aircraft turbine engine comprising at least one stator part (13) according to any one of claims 8 to 10. Module according to claim 11, characterized in that it is a compressor, preferably high pressure. 13. Aircraft turbine engine comprising at least one module (1) according to claim 11 or claim 12. 25